1. Field of the Invention
The invention relates to an internal combustion engine having a variable valve actuation device and a method for calculating an intake amount in the same engine.
2. Description of the Related Art
Japanese Laid opened Patent Application No. JP-2001-159323 discloses a valve actuation device that is provided for lifting intake valves and is capable of varying the amount of opening (the maximum valve lift and the working angle) of the intake valves (hereinafter, the device will be referred to as “variable valve actuation device”). In such variable valve actuation device-equipped engines, the amount of air taken into the combustion chambers (amount of intake air) is controlled by controlling the amount of opening of the intake valves.
For the control of the amount of intake air though the control of the amount of opening of the intake valves, detection of the amount of intake air via an intake amount sensor or the like is performed. However, in some states of operation of the engine, the amount of intake air detected by the intake amount sensor does not agree with the actual amount of intake air, due to the pulsation of air preceding the suction into the combustion chambers or a response delay of the intake amount sensor. Therefore, in the technology described in the aforementioned patent literature, the amount of intake air is determined through a calculation based on the closing timing of the intake valves and the engine rotation speed.
Thus, in the case where the amount of intake air is controlled by controlling the amount of opening of the intake valves, the amount of intake air detected by via an intake amount sensor or the like may deviate from the actual amount of intake air, depending on the state of operation of the engine. That is, in order to accurately detect the amount of intake air in the case where the amount of intake air is controlled through the control of the amount of opening of the intake valves, it is necessary to detect the amount of intake air by a measure other than the detection via such a sensor as an intake amount sensor or the like. Accordingly, it is an object of the invention to accurately detect the amount of intake air in an internal combustion engine equipped with a variable valve actuation device.